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Rice is widely grown after harvesting of oilseed rape (Brassica napus L.) in many countries. Experiments were carried out under greenhouse and field conditions to assess the impact of oilseed rape straw mulch on rice and paddy weeds. Oilseed rape mulch (900 g m −2 ) from straw 1-to-7 cm long was found to be safe for rice, when applied four days after sowing (DAS) in direct-seeded rice or four days after transplanting (DAT). In the meantime, the biomass of Echinochloa crus-galli (L.) P. Beauv. was reduced 65.74%, 80.18%, 81.15%, 70.99%, 55.65%, and 27.22%, respectively, when mulched with powder, and 1, 3, 5, 7, and 9-cm long oilseed rape straw, respectively, and the biomass reductions in Leptochloa chinensis (L.) Nees., Ludwigia prostrata Roxb., Ammannia auriculata Willd., and Cyperus difformis L. were all above 97% when mulched with 1 cm-length straw. The results of a field trial confirmed that oilseed rape straw mulch (900 g m −2 ) of 1 cm length was safe for rice. Moreover, weed suppression was as effective as the standard herbicide (oxadiargyl + butachlor 525 g ai ha −1 ) treatment. These findings demonstrate the potential to manage paddy rice weeds in an effective and environmentally sound manner by mulching with the straw of a preceding crop, oilseed rape. Keywords: crop safety; Brassica napus L.; Oryza sativa L.; straw mulch; weed suppression IntroductionRice (Oryza sativa L.) is the main cereal grain crop grown in the world and is the staple food for more than half of the world's population, including 65% of the Chinese population [1]. In 2017, 214 million tons of rice were produced on more than 31 million hectares (ha) in China, accounting for 27.9% of global rice production [2]. The traditional method of paddy farming in China is through manual transplanting of rice seedlings in fields. However, the proportion of direct-seeded rice increased from 2% of the total rice area in 2000 to about 11% in 2009; and during this same period, mechanical transplanting increased from 2% to nearly 13% of the total rice area in China [3].Weeds can compete with crops for nutrients, light, moisture, and space, resulting in reduced crop quality and yield [4]. In China, weeds threaten more than 15 million ha planted to rice, accounting for 45% of the total rice planting area [5]. Globally, rice yield losses due to weeds are estimated at

Geosmin and 2-methylisoborneol (2-MIB) are the most widespread sources of muddy flavours in freshwater. Both are secondary metabolites produced by microorganisms (Jiang et al., 2007). The employment of quantitative real-time PCR (qPCR) analysis allows the identification and quantification of the geoA and 2-MIB synthase genes, which encode for geosmin and 2-methylisoborneol